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Quizzes > Science

What Is True for Fastidious Organisms? Microbiology Quiz

Quick, free fastidious microbiology quiz to test your knowledge. Instant results.

Editorial: Review CompletedCreated By: Nidhi MehraUpdated Aug 26, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art illustration showing bacteria shapes and quiz lettering on teal background inviting microbial growth challenge

This quiz helps you identify what is true for fastidious organisms, from nutrient needs to culture media. You will answer quick questions on supplements and incubation, then see where to review. To compare growth preferences, explore barophile growth conditions or brush up on facultative anaerobe definition as you study related factors.

What term describes bacteria that need specific nutrients or growth factors from their environment to grow in the lab?
Fastidious
Autotrophic
Halophilic
Thermophilic
Fastidious bacteria have complex nutritional requirements and often need specific growth factors or enriched media to proliferate. They cannot synthesize certain essential nutrients and depend on the environment or added supplements. This term distinguishes them from organisms with minimal requirements. .
Which type of culture medium provides lysed red blood cells to support the growth of fastidious organisms?
Chocolate agar
MacConkey agar
Mannitol salt agar
Sabouraud dextrose agar
Chocolate agar is created by heating blood agar to lyse red blood cells, releasing intracellular nutrients such as X (hemin) and V (NAD) factors. These released factors support the growth of many fastidious organisms. This enriched medium is commonly used for Haemophilus and Neisseria species. .
Which genus of bacteria is prototypically fastidious and requires both X and V factors for growth?
Escherichia
Haemophilus
Bacillus
Clostridium
Haemophilus species, such as H. influenzae, require both hemin (X factor) and NAD (V factor) for growth on agar. They will not grow on standard blood agar unless these factors are supplied. This need makes them classic examples of fastidious organisms. .
Which environmental condition is required by capnophilic organisms, many of which are fastidious?
High salt concentration
Elevated carbon dioxide
Alkaline pH
Anaerobic atmosphere
Capnophiles are organisms that require increased levels of carbon dioxide, typically around 5 - 10%, for optimal growth. Many fastidious pathogens, such as Neisseria and some Haemophilus species, are capnophilic. Standard atmospheric conditions may not support their growth without added CO?. .
Fastidious bacteria often require preformed growth factors. Which of the following is a common growth factor they require?
Amino acids and vitamins
Agar
Polypeptides
Sodium chloride
Fastidious bacteria lack the ability to synthesize certain essential nutrients like amino acids and vitamins. They must obtain these preformed growth factors from the culture medium or host. This requirement distinguishes them from bacteria that are prototrophic. .
Bordetella pertussis is a fastidious organism. Which agar medium is commonly used to cultivate it?
MacConkey agar
EMB agar
Lowenstein - Jensen medium
Bordet - Gengou agar
Bordet - Gengou agar contains potato infusion, glycerol, and blood, creating an enriched environment for B. pertussis. This medium supports the growth of this fastidious pathogen while suppressing many others. It remains a standard for pertussis culture. .
What is the phenomenon called when Haemophilus species grow around Staphylococcus aureus colonies on blood agar due to extracellular NAD release?
Antagonism
Quorum sensing
Satellite phenomenon
Synergism
The satellite phenomenon occurs when Staphylococcus aureus lyses red blood cells, releasing NAD, which Haemophilus species require. Haemophilus then forms small colonies, or satellites, around the Staph colonies on blood agar. This diagnostic pattern helps identify factor V dependency. .
Legionella pneumophila is fastidious and requires which of the following components in its specialized growth medium BCYE?
Sabouraud dextrose
High salt concentration
Bile salts
L-cysteine and iron
Buffered charcoal yeast extract (BCYE) agar is supplemented with L-cysteine and iron, both of which are essential for Legionella growth. The charcoal neutralizes toxic compounds and the yeast extract provides other nutrients. This medium is the gold standard for isolating Legionella. .
Mycoplasma pneumoniae lacks a cell wall and requires which supplement in its growth medium?
Cholesterol
Hemin
NAD
Cysteine
Mycoplasma species incorporate cholesterol into their cell membranes because they lack a cell wall. Cholesterol is typically supplied in the medium via serum or defined supplements. Without it, Mycoplasma cannot maintain membrane integrity. .
Which feature explains why Chlamydia species, obligate intracellular bacteria, cannot be cultured on standard artificial media?
They are acid-fast
They need high salt conditions
They produce endospores
They require living host cells for energy and nutrients
Chlamydia species depend on host cell ATP and other metabolites because they lack complete metabolic pathways. They can only replicate within living eukaryotic cells. Attempted culture on synthetic media fails due to these metabolic deficiencies. .
Fastidious bacterial pathogens often have reduced biosynthetic capabilities. What genomic trait is commonly observed in such organisms?
Expanded gene families
Large genomes rich in repeats
Multiple plasmids carrying virulence factors
Genome reduction with loss of metabolic genes
Many fastidious pathogens undergo genome reduction, losing genes for amino acid, vitamin, or cofactor biosynthesis because they obtain these from the host. This streamlining leads to smaller genomes and increased host dependency. It is a hallmark of intracellular and symbiotic bacteria. .
In the context of Haemophilus influenzae growth factors, which statement is true regarding factor V (NAD)?
It is heat-stable and unaffected by boiling
It is identical to hemin
It is heat-labile and destroyed by boiling
It can be synthesized by the bacterium
Factor V (NAD) is heat-labile and is destroyed by boiling or autoclaving. As a result, media must be prepared carefully to retain V factor for Haemophilus growth. Hemin (X factor) is heat-stable and not affected by the same conditions. .
Which laboratory test determines if Haemophilus species can synthesize heme and thus identifies X factor requirements?
Oxidase test
Porphyrin test
Coagulase test
Catalase test
The porphyrin test assesses a bacterium's ability to convert delta-aminolevulinic acid into porphyrins, precursors of heme. A positive test indicates no requirement for the X factor (hemin). A negative test implies that the organism is X factor dependent and must obtain heme exogenously. .
Mycobacterium tuberculosis, a fastidious organism, is commonly cultured on which medium?
MacConkey agar
Chocolate agar
Lowenstein - Jensen medium
Blood agar
Lowenstein - Jensen medium is egg-based and contains malachite green to inhibit contaminants while supporting M. tuberculosis growth. This medium fulfills the organism's slow and fastidious growth requirements. It remains a standard for tuberculosis culture in diagnostic labs. .
Which fastidious bacterium cannot be cultured on routine laboratory media and requires animal or cell culture systems for propagation?
Staphylococcus aureus
Treponema pallidum
Escherichia coli
Bacillus subtilis
Treponema pallidum, the causative agent of syphilis, does not grow on artificial media and must be propagated in animal hosts or specialized cell culture systems. Its fastidious nature and delicate structure prevent routine culture. Diagnosis often relies on serology or direct visualization. .
Which component in BCYE agar is essential for the growth of Legionella pneumophila?
Bile salts
Polymyxin B
L-cysteine
Lactose
BCYE agar includes L-cysteine because Legionella lacks the biosynthetic pathways to produce this amino acid. Without L-cysteine, the organism cannot grow. The medium also contains iron and yeast extract for additional nutrition. .
Campylobacter jejuni is microaerophilic. What atmospheric conditions does this bacterium require for optimal growth?
5% oxygen, 10% carbon dioxide, balance nitrogen
Ambient air
High humidity only
Strict anaerobic
Campylobacter jejuni grows best under microaerophilic conditions, typically 5% O?, 10% CO?, and 85% N?. These conditions mimic the intestinal environment of its animal hosts. Standard atmospheric oxygen levels are inhibitory to its growth. .
Fastidious bacteria often exhibit genome reduction. Which of the following best explains this phenomenon?
Duplication of ribosomal RNA genes
Gain of antibiotic resistance genes
Horizontal gene transfer increases genome size
Loss of genes encoding metabolic pathways due to host dependency
Genome reduction in fastidious bacteria results from the loss of genes for biosynthesis of amino acids, vitamins, and other metabolites that they can obtain from their host or environment. This streamlining enhances dependency but reduces metabolic burden. It is common among obligate intracellular pathogens. .
Coxiella burnetii, the causative agent of Q fever, is notoriously fastidious. Why is it difficult to cultivate in vitro?
It only grows at extremely high temperatures
It is resistant to all common agar components
It forms endospores inhibiting growth
It requires acidified vacuole-like conditions and specialized media
Coxiella burnetii replicates within acidified phagolysosomal vacuoles in host cells, requiring media that mimic these low pH conditions. Standard neutral pH media are insufficient. Specialized cell culture or acidified media are needed for laboratory cultivation. .
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Study Outcomes

  1. Identify True Traits of Fastidious Organisms -

    Use this microbial growth quiz to pinpoint which is true for fastidious organisms and recognize their hallmark characteristics.

  2. Explain Nutrient Preferences -

    Describe how specific bacterial growth requirements influence fastidious organisms characteristics, including essential vitamins and growth factors.

  3. Differentiate Growth Conditions -

    Compare optimal microbe growth conditions for fastidious versus non-fastidious bacteria to understand their laboratory cultivation needs.

  4. Analyze Lab Cultivation Factors -

    Assess temperature, pH, and atmospheric requirements to determine the best culture environment for fastidious microbes.

  5. Apply Knowledge to Experimental Design -

    Use insights from the quiz to design experiments that meet the precise bacterial growth requirements of fastidious organisms.

Cheat Sheet

  1. Enriched Media Dependence -

    Fastidious organisms require additional nutrients like heme, NAD, or vitamins to grow, making them unable to thrive on standard agar. This enriched media dependence is a core fastidious organisms characteristic demonstrated by pathogens such as Neisseria and Haemophilus (CDC, ASM). A handy mnemonic is "Fast food doesn't grow here" to remember that these bacteria can't survive on basic media alone.

  2. Specific Growth Factors -

    Which is true for fastidious organisms? They often depend on precise growth factors such as amino acids, nucleotides, or specific ions that must be added to culture media. University of Oxford studies highlight how supplementing media with L-cysteine or glutathione can dramatically increase the yield of bacteria like Legionella pneumophila.

  3. Atmospheric Requirements -

    According to CLSI guidelines, many fastidious microbes grow best under microaerophilic or capnophilic conditions, requiring 5 - 10% CO2 and reduced O2 levels. Candle jar incubation is a classic method used in labs to achieve the correct atmosphere for Neisseria gonorrhoeae. This knowledge is crucial in a microbial growth quiz to identify microbe growth conditions.

  4. Slow Generation Times -

    Fastidious bacteria often have longer generation times, meaning they divide more slowly than non-fastidious species, which affects incubation duration and underscores critical bacterial growth requirements (Journal of Bacteriology). For example, Bordetella pertussis may take up to 7 days to form visible colonies on Bordet-Gengou agar. Remember: "Slow and steady wins the race" applies here as you wait for colonies to appear.

  5. Diagnostic Culture Techniques -

    Selective and differential media such as Thayer-Martin agar help isolate fastidious organisms by inhibiting contaminants and supplying required nutrients, showcasing precise bacterial growth requirements (ASM protocols). Observation of satellite growth around Staphylococcus aureus streaks on blood agar is a classic lab phenomenon for Haemophilus species. This technique is essential in microbial growth quiz questions and clinical microbiology protocols.

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